1. Field of the Invention
The present invention relates to a method of raising a structure while sustaining very large pressure due to same and then temporarily supporting the structure, and a wedge-type jack apparatus for use in the method, for the purpose of repairing or replacing supports or the like interposed between structures, such as bridges, and substructures.
2. Description of Prior Art
As shown in FIG. 9, between a structure A, such as a bridge or express highway, now under a completed condition and a substructure B, there are interposed supports C made of metal, etc., one at either of opposite ends of the substructure B in a lengthwise direction, for certainly transmitting to the substructure B not only vertical loads including the dead load of the structure A and the active load due to passage of vehicles, etc., but also various horizontal loads acting in a direction perpendicular to the vertical bridge axis due to earthquakes, winds, etc. The supports C must be repaired or replaced, as required, because they will deteriorate with time for many factors such as cracks caused by distortion and bending stress due to the load of the structure A, vibration, etc., as well as corrosion caused by rain, antifreezing mixtures, etc.
To data, therefore, the support C has been repaired or replaced as follows. Specifically, a plurality of metal plates or steel saddles are first piled up near the support C to a level substantially equal to that of the support C, thereby providing a temporary receiving member D. An ordinary hydraulic jack I capable of raising the structure A is then installed near the support C in a gap between the structure A and the substructure B. The jack I is operated to jack up the structure A until it detaches slightly away from the support C. Then, additional metal plates or the like are piled up on the temporary receiving member D to temporarily support the structure A. Under this condition, the support C is removed and repaired or replaced, followed by setting the repaired or new support in the original position. The jack I is operated to once jack up the structure A again for removing the temporary receiving member D, and then jack down it to the original condition. However, the ordinary jack I is required to be large in capacity in order to raise the structure as heavy as several hundreds through several thousands tons near its supporting point. Such ordinary jack I of large capacity can rarely be installed in the gap between the structure A and the substructure B, and is given with a too narrow space for installation. In practice, the length between the support C and a shoulder edge J of the substructure B, i.e., the edge-to-edge distance, is about 10-30 cm, and the height of the support C, e.g., bearing plate support, is about 10-20 cm. In addition, since the support C is usually installed in an elevated place as high as several meters through several tens meters, installation of the jack of large capacity cannot be performed by only human power and may entail risk. When the jack of large capacity is lowered from the bridge using a crane, it has been unavoidable to suspend traffic of vehicles temporarily. Moreover, attached to the lower central surface of the structure A and adjoining regions are girders for reinforcing the structure A, pipings and other attachments in lengthwise and crosswise directions, leaving no space between the supports C and C to install the jack. Accordingly, the repair or replacement work has been unable to perform in some cases.
For the reason, there has been proposed a so-called bracket method. Specifically, as shown in FIG. 10, the temporary receiving member D comprising metal plates or the like are first interposed with height substantially equal to the gap between the structure A and the substructure B. A bracket E made of metal or other material is then fixed to a side wall of the substructure B in an appropriate position by bolts or the like. The ordinary jack I is installed on the bracket E and operated to jack up the structure A by about several millimeters. Under this condition, additional metal plates are placed on the temporary receiving member D to increase its height corresponding to a gap between the temporary receiving member D and the jacked-up structure A, for thereby supporting the structure A temporarily. Then, the support C is removed and repaired or replaced. The ordinary jack I is operated to jack up the structure A again to remove the temporary receiving member D, followed by jacking down it to the original condition.
Alternatively, there has also been proposed a so-called steel bent method. Specifically, as shown in FIG. 11, a foundation F made of concrete or the like is formed on the ground immediately adjacent the substruction B with an intention to extend the substructure B. A steel scaffold G is vertically built up to a level almost equal to the top of the substructure B. A temporary substructure H is set to make a horizontal plane at the top of the steel scaffold G, and the ordinary jack I is installed on the temporary substructure H. Then, in a like manner to the above, the jack I is operated to jack up the structure A for supporting it temporarily.
The above methods are only examples to cope with the hard situations. In some cases, dependent on installation place or size of the support, the ordinary hydraulic jack I cannot be installed in the gap between the structure and the substructure, and the level of the structure is too high to carry out the work of installing the ordinary jack. In other cases, although an ample gap is present between the structure and the substructure, the base area is too small for installation of the ordinary jack I. These relevant problems are summarized below.
".circle." to raise a heavy structure as much as several several hundreds through several thousands tons near its supporting point, while keeping the current condition unchanged, requires the ordinary jack I of large capacity. Such conventional ordinary jack I of large capacity cannot be sometimes installed in the gap between the structure and the substructure, and hence cannot be employed for raising the structure directly. Even if can be installed, the resulting small working area causes inconvenience because both the temporary receiving member and the ordinary jack I must be installed near the support on the substructure. PA0 ".circle." For safety, to raise a structure of, e.g., 100t requires a jack with the maxium power of about 150t taking into consideration of a safety factor. Because a cylinder of the ordinary jack I is in the form of column, the load is applied to the region near the shoulder edge J of the substructure B as shown in FIG. 9. This leads to a fear that the region near the shoulder edge J of the substructure B may fatigue and break down. PA0 ".circle." When jacked up, it is enough to raise the structure to such an extent that the structure detaches away from the support by several millimeters. Since the ordinary jack I, in place of the support, is subjected to vertical and horizontal loads and vibration transmitted from the structure and so on during repair of the support, the structure cannot be sustained by the ordinary jack I alone for a long period. To this end, the temporary receiving member requires to be interposed between the structure and the substructure. Therefore, the structure is once jacked up to an excessively lifted state, i.e., a level inclusive of the excessively lifted amount taking into account a sink, fit, etc. which will occur with time after installation of the temporary receiving member. However, lifting the end of the structure too excessively causes a warp in the structure, resulting in a risk that the floor concrete may crack near a cross girder at the end. PA0 ".circle." When jacked down, the ordinary hydraulic jack I is difficult to adjust a reduction in the hydraulic pressure. This causes the structure to be lowered abruptly by its dead load, making it hard to control jack-down. PA0 "501 " Usually, since vehicles and so on are passing over the upper surface of the structure even during repair of the support, the step difference between the concerned structure and the adjacent structure must be in order of 10 mm for safety, presenting a limitation in the raised height of the former. Therefore, precise operation is needed in raising the structure to reduce the step difference. But, it is difficult to finely adjust raising control by the ordinary hydraulic jack I, resulting in a fear that some error may occur when raising the structure. PA0 ".circle." Where the support is installed over the surface of a river, sea, etc., a working ship or the like is located under the support and then the support is repaired using a crane equipped on the ship. This leads to the large-scaled work and takes considerable cost and time. PA0 ".circle." The ordinary jack I has a large weight and is difficult to move by human power for installation. Further, because the relatively high jack is vertically mounted, there is a risk that the jack may turn over and drop due to earthquakes or vibration. This will invite a serious accident. PA0 ".circle." The bracket method, steel bent method, etc. need a great deal of time and cost to prepare the temporary sub-structure before raising of the structure. PA0 ".circle." While the structure is resting on the ordinary jack or the temporary receiving member, the upper surface of the structure is subjected to active loads due to passing vehicles and so on in lengthwise and crosswise directions. There is a risk of serious accident that the structure may drop off the ordinary jack or the temporary receiving member during the work.
The present invention is intended to solve the problems as mentioned above, and to provide a method of raising a structure while sustaining very large pressure due to same and then temporarily supporting the structure by the use of a wedge-type jack which can safely raise the structure directly irrespective of the installation place of a support, and a wedge-type jack apparatus for use in the method.